As Pope, John XVIII occupied his time mainly with details of ecclesiastical administration. He authorized a new Diocese of Bamberg to serve as a base for missionary activity among the Slavs, a concern of Henry II's. He also adjudicated a squabble between the abbot of Fleury and the bishops of Sens and Orléans.[1]

Ultimately he abdicated and, according to one catalog of Popes, retired to a monastery, where he died shortly afterwards. His successor was Pope Sergius IV.

Confusion over ordinals

Pope John XVIII was only the 17th pope called John, because John XVI (997–998) was an antipope according to official reckoning. His status as an antipope was not recognized at the time, however, so the true 16th Pope John called himself John XVII. The true 17th pope called John took the regnal number XVIII. The true sequence of numbering has never been corrected.